The arrangements already known for securing two bodies wherein the thermally-induced stresses are to be minimized utilize in large measure radially yielding connecting members which constitute an otherwise rigid connection. European Patent publication No. 00 63 063 discloses a radio telescope wherein one connecting point is maintained while other connecting points each permit a change in radial direction. Here, radially yielding attachment members are used which function in the manner of leaf springs.
It is also known to attach a glass mirror to a metal supporting structure by means of radially flexible elements. In this connection, reference may be made to the proceedings of the International Society for Optical Engineering, volume 250 (1980), pages 24 to 26 and volume 450 (1983), pages 34 to 38. This type of attachment leads to very complicated attachment systems which in addition lead to a certain inclination to oscillate.
Also, German Pat. No. 31 19 299 discloses an attachment achieved by means of an elastic adhesive connection. However, the use of cementing technology has several disadvantages. On the one hand, an ideal cement thickness of zero is not attainable while, on the other hand, the locations where the cement is applied have a reduced stiffness and are not releasable.
German Pat. No. 30 12 830 discloses the correction of surface deformations by means of piezo-electric material with an active adjustment occurring.
From German Pat. Nos. 10 10 802 and 25 58 625 it is known in the area of machine tools to provide a compensation of thermal expansion by means of expansion rods. This construction technique leads to a very large configuration and is only effective at points. This principle is also utilized in the area of clock pendulums.
Many types of attachment have the disadvantage that thermal expansion causes a displacement of the attachment points. This disadvantage being either that constraining forces can be transmitted from the structure of the carrier to the component or that the stiffness of the connection is minimal. Impermissible deformations can even occur with relatively small constraining forces whereby the utilization is no longer present or at least very greatly reduced. In the application of optical elements such as telescope mirrors, very high requirements are imposed upon their surface contour and these requirements can lie in the range of several nanometers. Especially in optical elements of this kind, even low forces lead to determinable deformations of the surface which greatly reduce the usability of the optical component. If additional increased rigidity and strength requirements are imposed, the above-described attachment methods cannot fulfill the requirements.
German Pat. No. 918,051 discloses a compensation body which is dimensioned and arranged so that changes in length of a supporting structure and a compensating body induced by temperature influences cancel each other with reference to a measurement distance. Two measurement legs with compensating rods are provided at the ends of this supporting structure. As disclosed in the introduction of German Pat. No. 918,051, this invention utilizes two materials having different coefficients of expansion for the purpose of matching the coefficients of expansion.
Furthermore, clamping connections are generally known. Thus, wedge-shaped tie rods are known in the furniture industry where they are utilized for connecting, for example, individual parts of a cabinet.